The present invention relates to inkjet printhead chip layouts and, more specifically, to ink jet printhead chips having an asymmetric layout wherein the heaters and TAB bond pads are located on opposing edges, and to inkjet printhead assemblies.
Ink jet printers typically include recording heads, referred to hereinafter as printheads, that employ transducers which utilize kinetic energy to eject ink droplets. For example, thermal printheads rapidly heat thin film resistors (or heaters) to boil ink, thereby ejecting an ink droplet onto a print receiving medium, such as paper. According to this ink jet method, upon firing a resistor, a current is passed through the resistor to rapidly generate heat. The heat generated by the resistor rapidly boils or nucleates a layer of ink in contact with or in proximity to a surface of the resistor.
The nucleation causes a rapid vaporization of the ink vehicle, creating a vapor bubble in the layer of ink. The expanding vapor bubble pushes a portion of the remaining ink through an aperture or orifice in a plate, so as to deposit one or more drops of the ink on a print receiving medium, such as a sheet of paper. The properly sequenced ejection of ink from each orifice causes characters or other images to be printed upon the print receiving medium as the printhead is moved relative to the print receiving medium.
Typically, the orifices provided on such a plate are arranged in a pair of linear arrays. Moreover, the paper is typically shifted each time the printhead moves across the paper. The thermal ink jet printer is generally fast and quiet, as only the ink droplet is in contact with the paper. Such printers produce high quality printing and can be made both compact and economical.
There are many performance issues that should be considered when designing inkjet printers. Many of these issues are tied to the inkjet technology and, more specifically, to the design of the chips used in the printheads. In many regards, the printhead chip architecture and design dictates the overall performance of the printer.
Overall, however, the performance goals of printhead chip design must also be balanced with meeting cost and manufacturability requirements. For example, the cost of processed silicon is a first order function of chip area. Therefore, in order to minimize cost, the area of any chips used in the printhead should be minimized.
Conventional printhead chip architectures, such as those shown in FIGS. 1A and 1B, target specific design requirements, but have certain limitations. For example, center via ink feed chips 111 might ease printhead assembly, but the center via 116 takes up valuable area on the chip and makes the chip prone to cracking. Moreover, additional area on the chip is also required to wire the control and drive signals of the chip around the via 116, as represented by chip wiring 121.
Edge ink feed designs (commonly referred to as xe2x80x9cedgefeedsxe2x80x9d), such as those utilized by the chip 211 shown in FIG. 1B, have arisen as an alternative to center via ink feed designs. Edgefeeds do not have a via, but rather have heaters 224 on opposing edges of the chip 211, with interconnects 270 on opposing ends of the chip. Accordingly, as there is no center via, less area on the chip is wasted, and the chips 211 are not as prone to cracking.
Typically, interconnects 270 (e.g., TAB bond pads) and their corresponding beams 271 (e.g., beams coming from a TAB circuit) must be protected from the ink, such as by covering them with encapsulant 272 for example. These areas of applied encapsulant 272 generally constitute the points on the printhead 210 that will come the closest to contacting the print receiving medium 232 as it is passed by the printhead. Therefore, as shown in FIG. 2, to avoid smearing any ink applied to the print receiving medium 232, it is desirable to maintain an appropriate gap (G) (commonly referred to in the art as the xe2x80x9cpaper gapxe2x80x9d) between the print receiving medium and the printhead 210.
The distance (D) over which the paper gap (G) must be maintained is commonly referred to in the art as the critical paper gap control region. As can be understood, ensuring a proper paper gap (G) becomes more difficult as critical paper gap control regions (D) increase. For example, because the interconnects 270 in conventional edgefeeds are placed at the ends of the chip 211, there is a substantial distance between areas of encapsulant 272. As these areas of encapsulant 272 define a substantial critical paper gap control region (D), controlling the paper gap (G) in printers utilizing conventional edgefeed printhead chips 211 can often be difficult.
Moreover, inkjet printers typically utilize devices, such as an exit roller or star wheel 238, for example, to maintain the paper gap (G). The distance (M) the print receiving medium 232 must travel past the last appropriate nozzle position (N) on the printhead 211 in order to be held at the desired paper gap (G) over the critical paper gap control region (D) (e.g., the distance the print receiving medium must travel to effectively reach a device such as device 238), is commonly referred to in the art as the minimum print margin. The minimum print margin (M) defines, for example, how close to an edge of the print receiving medium 232 the printer can print without potentially experiencing print quality problems. As can be understood from FIG. 2, because of the additional area on the printhead required to bond (and encapsulate) the relevant portions of the connecting circuit (not shown) to the interconnects (not shown) of the chip 211, printers using conventional edgefeed printhead chips typically also suffer from larger minimum print margins (M).
Accordingly, it would be advantageous to have an inkjet printhead chip design that has reduced dimensions. Moreover, it would be advantageous to have an inkjet printhead chip design that could retain the benefits of a conventional edgefeed design, while minimizing the critical paper gap control region (D). Furthermore, it would be desirable to have an inkjet printhead chip design that retains the benefits of conventional edgefeed designs while minimizing the minimum paper margin (M).
Accordingly, it is an object of the present invention to provide printhead chips that overcome problems associated with conventional chips.
It is another object of the present invention to provide inkjet printhead chips that minimize the critical paper gap control region (D) in the printer in which it is used.
It is a further object of the present invention to provide printhead chips that minimize the minimum paper margin (M) in the printer in which it is used.
Still another object of the present invention is to provide printhead chips that are easy to manufacture and assemble.
Yet a further object of the present invention is to provide inkjet printhead chips that have a minimized chip area.
Still another object of the present invention is to provide printhead chips with improved operational characteristics.
A further object of the present invention is to provide printhead chips that are inexpensive to produce.
According to one embodiment of the present invention, an inkjet printhead chip comprises a substrate, a plurality of transducers, a plurality of interconnects and driver circuitry capable of electrically connecting the transducers and the interconnects. The plurality of transducers are arranged along a first edge of a surface of the substrate. Meanwhile the plurality of interconnects are arranged along an opposing second edge of the surface of the substrate. The driver circuitry is arranged on the substrate.
Preferably, the plurality of transducers are capable of receiving ink along the first edge. In one embodiment of the present invention, the transducers are capable of receiving ink only along this first edge. More preferably, a plurality of transducers are arranged only along the first edge, while the plurality of interconnects are arranged only along the second edge.
In further preferred embodiments, the substrate is substantially integral and the driver circuitry comprises switchable addressing circuitry. For example, the switchable addressing circuitry comprises transistors and/or multiplexing circuitry, and preferably comprises transient addressing circuitry. In addition, the driver circuitry comprises a plurality of conductive leads arranged on the substrate generally perpendicular to the second edge.
Still another preferred embodiment of the present invention separates each of the transducers from adjacent transducers by less than {fraction (1/300)} of an inch. More preferably, each of the transducers is separated from adjacent transducers by approximately {fraction (1/600)} of an inch. The transducers can comprise piezoelectric elements, although heater resisters are preferred.
In a preferred embodiment, the plurality of transducers extend along the first edge for a transducer length. Meanwhile the plurality of interconnects extend along the second edge for an interconnect length, wherein the transducer length is at least as long as the interconnect length. In a further preferred embodiment, the transducer length is approximately equal to the interconnect length.
In another embodiment of the present invention, an inkjet printhead assembly comprises a body and a printhead chip assembly arranged on a print surface of the body. The print surface is capable of being arranged generally parallel to a surface of a print-receiving medium. The printhead chip assembly according to this embodiment includes a substrate, an edge feed, at least one chamber, and a plate.
The substrate according to this embodiment has a surface with opposing first and second edges, a plurality of transducers arranged along the first edge and a plurality of interconnects arranged along the second edge. The edge feed is disposed between the first edge and the printhead body and is in fluid communication with an ink reservoir of the body. The at least one chamber is in fluid communication with the edge feed and the plate is provided with a plurality of apertures, each aperture being capable of cooperating with at least one of the at least one chambers to allow ink to be ejected from said chambers.
Preferably, the printhead chip assembly is arranged adjacent to an end of the print surface. More preferably, the substrate surface further comprises opposing ends, one of which being adjacent the end of the print surface. In yet another preferred embodiment of this invention, the printhead chip assembly comprises only one substrate.
In a preferred embodiment, the inkjet printhead is capable of causing ink to be ejected onto the print-receiving medium within a print swath height. In addition, the plurality of interconnects extend along the second edge for an interconnect length, wherein the swath height is at least as long as the interconnect length. More preferably, the interconnect length is less than the swath height.
A further preferred embodiment comprises an encapsulant generally covering the plurality of interconnects and extending along the second edge for an encapsulant length. According to one embodiment, the swath height is at least as long as the encapsulant length. More preferably, the encapsulate length is less than the swath height,
In yet another embodiment of the present invention, an inkjet printhead capable of causing ink to be ejected onto a print-receiving medium within a print swath height is provided. The inkjet printhead comprises a body and a printhead chip assembly. The body has an ink reservoir and a print surface capable of being arranged generally parallel to a surface of a print-receiving medium. Meanwhile, the printhead chip assembly is arranged on the print surface adjacent an end of the print surface.
In this embodiment, the printhead chip assembly comprises a single substantially integral substrate, an edge feed, at least one chamber, and a plate. The substrate has a surface with opposing first and second edges, a plurality of the transducers are arranged only along the first edge and a plurality of interconnects are arranged only along the second edge, wherein the plurality of interconnects extending along the second edge extend for an interconnect length that is less than the swath height. In addition, the edge feed is disposed between the first edge and the printhead body, and is in fluid communication with the ink reservoir. The at least one chamber is in fluid communication with the edge feed. In addition, the plate is provided with a plurality of apertures, each aperture being capable of cooperating with at least one of the at least one chambers to allow ink to be ejected from said chambers.
Still other aspects of the present invention will become apparent to those skilled in this art from the following description wherein there is shown and described various embodiments of this invention, simply by way of illustration. As will be realized, the invention is capable of other different aspects and embodiments without departing from the scope of the invention. Accordingly, the drawings and descriptions should be regarded as illustrative in nature and not as restrictive in nature.